Abstract
This paper firstly and experimentally demonstrates an in-fiber axial micro-strain sensing head, combined with a Mach-Zehnder interferometer (MZI) based on the concentric multilayer elliptical-core fiber (CMECF). This MZI with a high extinction ratio (about 15 dB) is successfully achieved with a CMECF-single mode fiber-CMECF (CSC) structure. The MZI sensor theory and the resonance demodulation technology are systematically described in this paper. In this CSC structure, two sections of the CMECF have a role as the mode generator and coupler, respectively. LP01 and LP11even, which have similar excitation coefficients, are two dominated propagating mode groups supported in the CMECF. On account of the distinct dual-mode property, a good stability of this sensor is realized. The detected resonance in the MZI shifts as the axial micro-strain variated due to the strong interaction between higher order modes. High sensitivity of ∼1.78 pm/με is experimentally achieved within the range of 0 με–1250 με, meanwhile, the intensity fluctuation is below 0.38 dB.
Highlights
Fiber-optic sensors exhibit several distinctive features such as low cost, compact size, high sensibility, anti-erosion, immunity to electromagnetic interference, and multiplexing capabilities, which draw a great deal of attention to strain measuring under harsh conditions
Many novel fiber sensing structures for strain induction have been reported, such as sensors based on fiber Bragg gratings (FBGs) [1,2,3], fiber long-period gratings (LPGs) [4, 5], Mach-Zehnder interferometers (MZIs) [5,6,7], fiber tapers [6, 7], Saganac [8], and Fabry-Perot (FP) [9, 10] structures
We demonstrate a novel concentric multilayer elliptical-core fiber (CMECF) and an axial micro-strain sensor based on a CMECF-single mode fiber-CMECF (CSC) structure
Summary
Fiber-optic sensors exhibit several distinctive features such as low cost, compact size, high sensibility, anti-erosion, immunity to electromagnetic interference, and multiplexing capabilities, which draw a great deal of attention to strain measuring under harsh conditions. Many novel fiber sensing structures for strain induction have been reported, such as sensors based on fiber Bragg gratings (FBGs) [1,2,3], fiber long-period gratings (LPGs) [4, 5], Mach-Zehnder interferometers (MZIs) [5,6,7], fiber tapers [6, 7], Saganac [8], and Fabry-Perot (FP) [9, 10] structures. In-fiber interferometic sensors show great advantages over the others in term of cost, stability, fabrication difficulty, and sensitivity. In-fiber sensors based on the multimode-singlemode-multimode (MSM) structure get good results on the convenient manufacture and high sensitivity.
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